DAKAR, July 26 (Thomson Reuters Foundation) - International aid agencies in Central African Republic have suspended operations in three towns amid escalating violence between armed factions and attacks on humanitarians, the United Nations said on Wednesday.

A surge in fighting in several hotspots - from Kaga Bandoro in the north to Bangassou and Zemio in the east - has uprooted more than 100,000 people since April in the worst spell of upheaval since the peak of the conflict in 2014, aid groups say.

The violence may plunge the country back into a humanitarian crisis four years after conflict first erupted, when Muslim Seleka rebels seized power, triggering reprisals by Christian "anti-balaka" militias, the U.N. aid chief said last week.

Militants have looted humanitarian compounds and attacked health facilities, halting the work of aid agencies such as the International Rescue Committee and Plan International, said the U.N. Office for the Coordination of Humanitarian Affairs (OCHA).

"Aid groups can't operate when staff are attacked and tortured in their compounds, and children are shot dead in hospitals," said Joseph Inganji, OCHA's country director.

Medical charity Medecins Sans Frontieres (MSF) suspended its operations in Zemio this month after militants killed a baby in a hospital hosting thousands of people displaced by violence.

"This is one of the world's most dangerous countries for humanitarians ... there is violence on an almost daily basis," Inganji told the Thomson Reuters Foundation by phone.

Aid workers have been attacked on about 60 occasions so far this year, compared with a total of 137 attacks in 2016, according to the latest figures from OCHA.

The withdrawal of aid and services in Bangassou, Kaga Bandoro and Zemio has left tens of thousands of people without enough to eat and unable to access healthcare - leaving them prey to malnutrition and disease, several aid groups said.

Violence has escalated in Central African Republic since former colonial power France ended its peacekeeping mission last year, despite the election in March 2016 of President Faustin-Archange Touadera, which raised hopes of reconciliation.

Thirteen of the 14 armed groups, along with representatives from the government, signed a peace deal last month, yet as many as 100 people were killed in the town of Bria, northeast of the capital Bangui, in factional fighting the very next day.

More than 1 million people are displaced - about half are living as refugees in neighbouring countries - and nearly one in two people - at least 2.2 million - need aid, according to OCHA. (Reporting By Kieran Guilbert, Editing by Lyndsay Griffiths.; Please credit the Thomson Reuters Foundation, the charitable arm of Thomson Reuters, that covers humanitarian news, women's rights, trafficking, property rights, climate change and resilience. Visit http://news.trust.org)